Introduction

The Sigma AF 50mm f/2.8 EX DG macro is a member of Sigma's popular gang of four macro
lenses. The new DG (Digital) variant features an improved lens coating optimized
for digital sensors. It is a full format lens but as usual we'll have a look how it performs
on an APS-C DSLR. Here the field-of-view of the lens is equivalent to 80mm on
full frame cameras. The primary application of the lens is, obviously, macro photography
but as with most macro lenses infinity focus is possible so its scope is naturally broader.

The optical construction is made of 10 elements in 9 groups without any special elements.
The aperture mechanism has 7 aperture blades. Typical for most true macro lenses the lens
features a floating system which corrects aberrations down to the max. magnification of 1:1
at a min. focus distance of 0.189m. The filter size is 55mm. With a weight of 320g and a size
of 71x67mm it is pretty small at infinity focus. The length of the lens grows substantially
when focusing towards closer distances as you may notice in the product image above.
The tiny barrel-shaped lens hood doesn't add much length on top. It's a screw-in
type variant so it's not really convenient to attach but combined with the non-rotating
front-element it remains possible to use a polarizer.

The construction quality feels very decent and the typical EX ("Excellence")
finish (crinkle style) provides a good grip. The rubberized focus ring operates smooth
(no wobbling whatsoever) but it isn't overly damped. The AF speed is okayish but there're
faster focusing lenses out there. There's a focus limiter which may help to avoid
excessive hunting towards the macro universe when using the lens at conventional
focus distances.